A model of contact sensitivity is being studied in the guinea pig using the hapten oxazolone, a non-toxic contact sensitizer. Guinea pigs were immunized by application of oxazolone to the skin or by injecting it intradermally in either incomplete or complete Freund's adjuvant. Animals were challenged with a drop of oxazolon on the skin and in the conjunctiva sac. The eyes were examined 24 hours later and removed for histopathologic examination. Reactions in the conjunctiva, cornea and ciliary body were rich in eosinophils and contained relatively few basophils while skin reactions contained may basophils and few eosinophils. These studies indicate that in addition to the skin, the conjunctiva and cornea participate in contact sensitivity and that eosinophils are prominent components of these reactions. A model of delayed hypersensitivity in the guinea pig conjunctiva is being studied by immunizing animals with protein antigens or bacterial extracts in complete or incomplete Freund's adjuvant. Subconjunctival challenges are made one to three weeks after immunization and eyes are examined daily. Tissues are being examined histopathologically at various time intervals. These studies are aimed at determining the pathogenesis of phlyctenulosis and hypersensitivity reactions to the staphylococcus. Penetrating keratoplasties are being performed in New Zealand white albino male rabbits. Pairs of rabbits are used, each donating 5.5 mm full-thickness graft to its mate. Grafts from two rabbits are exchanged and sutured into place with interrupted 10-0 nylon sutures. Animals are examined daily by slit lamp microscopy and sutures are removed as blood vessels begin to invade the graft-host junction. Graft rejection is induced by transplanting a 2 x 2cm full thickness piece of skin from the shaven flank of a rabbit and beneath panniculus carnosus of its mates abdominal wall. Following skin implantation, animals are being observed daily for signs of rejection. Animals are sacrificed at intervals ranging from 4 to 20 days following skin implantation and eyes are being studied by light microscopy. One micron sections are being cut, stained with Giemsa's reagent and differential cell counts are being performed.